Accrued Expense and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Compensation	$ 2,830	$ 2,875
Marketing services	109	949
Distribution agreements and managed care costs	1,330	959
Professional fees	926	291
Franchise taxes	53	52
Travel expenses	157	53
Manufacturing expenses	260	89
Other accruals	133	264
Total	$ 5,798	$ 5,532